A gas turbine is constituted by a compressor, a combustor, and a turbine. The compressor compresses air taken in from an air inlet, thereby generating high-temperature and high-pressure compressed air. The combustor supplies fuel to the compressed air to burn the fuel, thereby generating high-temperature and high-pressure combustion gas. In the turbine, a plurality of turbine vane and a plurality of turbine rotor blades are alternatively arranged in a casing. The turbine rotor blades are driven by combustion gas supplied to an exhaust passage, thereby rotating the rotor coupled to a power generator. The combustion gas that has driven the turbine is released into the atmosphere after being converted to a static pressure by a diffuser.
In such a gas turbine, in recent years, compressors use higher pressure, and air temperature at a discharge portion at a latter stage of the compressor becomes 500° C. or more. Therefore, as a conventional gas turbine, there has been known a gas turbine in which cooled air obtained by extracting a part of compressor discharge air and cooling the air via a cooler is fed into a hollow part (a cavity) provided in a load coupling that couples rotors of a compressor and a turbine to each other at a latter stage of the compressor to cool the temperature of the hollow part (see, for example, Patent Document 1).
Patent Document 1: Japanese Patent Application Laid-open No. H11-125199